Graham Platner won the Democratic primary for Senate in Maine and quickly turned his populist message against Susan Collins, the Republican incumbent.

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Graham Platner is seeking to make a Democratic nomination for U.S. Senate official in advance of one of the most anticipated contests of the year.

Any indication of tepid support for Graham Platner, a Democratic candidate for Senate in Maine, will be seen as a warning sign about his chances against Senator Susan Collins, the Republican incumbent.

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Primaries for U.S. Senate and U.S. House on Tuesday will set the stage for a midterm general election in which Maine is expected to play a critical role in deciding control of both chambers.